4 Stroke 4 Valves Over Head Camshaft Engine

General
A Overhead Camshaft engine is an internal combustion engine with the camshaft placed in the cylinder head.

This single cylinder model has four valves, with an engine capacity of 30 cc.
This model was designed in Tinkercad.
Dimensions:   120 x 95 x 180 mm.
Weight:  0.18 kg.
 

Printing and Assembly
The parts should be printed on a smooth build plate.
Try to avoid elephant foot.

I printed the model on a PRUSA MINI, with PLA+ filament, layer height 0.15 mm. 
Use Hard Plastic Glue where necessary.

A open and closed version of the cylinder head (E1.1 and E1.2) is included.

For assembled and exploded views, use “00-OHC Engine - ASSEMBLED.stl” ,  “01-OHC Engine - EXPLODED VIEW.stl” and Tinkercad screenshots.
Assembly is in alphabetical order (A1 → I2).
Printing tips are available for many parts.
A small amount of machine oil will help a smooth running of the assembled model.

By lifting the cylinder head, valve timing can be executed.

Metal parts
To join the cylinder head and cylinder to the crankcase, four M4 x 25 mm allen screws are needed.
As an alternative, you can place four round magnets (6 x 3 mm) in the top of the Cylinder and four round magnets (6 x 3  mm) in the bottom of the Cylinder Head to make the head easely removable from the cylinder. 

Four coil springs are needed for the valves, 10 mm width x 15 mm height. Wire thickness 0.6 or 0.7 mm (AliExpress).
 

Matching gearbox
A matching 2 speed gearbox can be found here: Constant Mesh Two Speed Gearbox by Bootjevaarder | Download free STL model | PrusaPrinters